1. Field of the Invention
The present invention relates to an image forming apparatus of an electronic photography type such as a copying machine or a laser printer, and more particularly to an improvement of a mechanism for automatically exhausting waste developing powder to a recovery vessel.
2. Background of the Invention
The inventors of the present invention know this type of image forming apparatus which is constructed to remove the toner left on a photosensitive body by using a cleaning device and recover the waste toner into a recovery vessel. If the developing powder stored in the developing bath has two kinds of components mingled, the carrier component is degraded earlier. It is, therefore, necessary to exhaust the degraded developing powder and exchange the waste developing powder with new powder.
The inventors of the present application know three related arts about the technique for recovering the waste toner and water developing powder. These three related arts are:
Japanese Patent Lying Open No. 60-153066 (Related Art 1) PA0 Japanese Utility Model Lying Open No. 63-180864 (Related Art 2) PA0 File Number 03-91-3102 (Related Art 3)
For a related art 1, a leased recovery vessel is mounted to the exhaust port of a developing bath. After checking for the recovery vessel, the exchange of the developing powder is started.
Since the related art 1 needs the leased recovery vessel, however, the leased recovery vessel entails idle operations such as transportation and storage of the vessel.
For a related art 2, the residual toner on a photosensitive body is removed by a cleaning device and is recovered in a recovery vessel. The waste developing powder in the developing bath is also recovered into the same recovery vessel.
The related art 2, however, does not have means for indicating how much of waste toner is now recovered in the recovery vessel. Though the recovery vessel is full of the waste toner, the situation may appear where the exchange of the degraded developing powder with the new powder is started. In this case, the waste developing powder is not allowed to be stored in the recovery vessel, that is, the waste is overflown from the recovery vessel.
For a related art 3, in a case that the waste developing powder is not overflown as is disclosed in claim 1, the waste is allowed to be recovered. Even if it is determined that the waste is overflown, no measures are suggested.